On Sundays there were a lot of children playing in the park,____parents seated together joking.

问题描述:

On Sundays there were a lot of children playing in the park,____parents seated together joking.
为什么填 they?独立主格结构 请仔细分析下,

填their.
独立主格省略BE动词,表达简便,具体定义不必再复制粘贴了.